11.7 Gardening insects and fungi

Attine ants in Central and South America have a rather unusual and ancient
relationship with a fungus generally called Leucocoprinus gongylophorus,
in the family Lepiotaceae (Basidiomycota). The relationship is a mutualism which
is thought to date back to about 45-65 million years ago. They actively
inoculate their nest with the fungus and then cultivate it by providing it with
pieces of leaves, pruning the hyphae and removing intruder fungi. As a
reward the fungus produces special structures, called gongylidia; hyphal
branches that have evolved to be eaten by ants. In Africa, some species of
termite also maintain a ‘garden’ of fungi belonging to the genus
Termitomyces (Order Agaricales, Basidiomycota). Nourished by the excrement
of the insects, the fungus digests dead plant material brought back to the nest
by the workers and provides more digestible food for the termites. We will
describe these mutualisms in detail in Chapter 15 (CLICK
HERE to view now), but we want to point out here that these are
gardening insects, and just as we cultivate particular
fungi for the food value of their fruit bodies,
gardening insects cultivate fungi for the food value
of the mycelium that results from its ability to digest plant remains.

Resources
Box

Leaf cutter ants

We have a short (8 minute) segment of video
(WMV-format) from the PBS (Public Broadcasting Service) documentary
“Evolutionary Arms Race” that illustrates the whole story of the
coevolution of the leafcutter ants, the fungi on which they feed, and the
bacteria they use to control the parasites that attack their garden.